Strip-shaped filter material with crimps molded in and filter elements made of this material

ABSTRACT

The instant invention provides a strip shaped filter material having a longitudinal plane with crimps molded therein for filtering a liquid or a gas comprising filter material being folded in a zigzag shape and having individual fold segments; said individual fold segments being held at a distance from one another via the crimps; said filter material having nondeformed filter strip segments adjacent to each crimp; said crimp having a zenith height; and the filter material having a thickness, in a cross section placed perpendicular to the longitudinal plane of the strip, which constantly decreases within the area of the crimps, starting from the nondeformed filter strip segments, up to the zenith height of the crimp, and that at the same time, the filter material is increasingly compressed in the direction of decreasing thickness.

The invention relates to strip-shaped filter material, especially filterpaper for liquid or gas filters, with crimps molded in, pursuant to thepreamble of claim 1, as well as filter elements made of these materials,pursuant to the preambles of claims 7 and 10.

Crimps in filter papers have always had semi-circular cross-sectionsuntil now (for example, DE-OS [German laying-out statement] 19 30 715).With such crimps, the paper thickness is always least at the transitionfrom the non-deformed level filter surface into the crimp, which canresult in material-related filtration problems at these sites, which areunder high static and dynamic stress during filter operation.

Filter elements made of strip material with crimps which is folded inzig-zags are also known, for example from DE-PS [German Patent] 12 48618.

To the extent that filter elements with crimped filter strip materialsare known beyond this, from DE-OS 19 22 976 and DE-OS 26 51 910, thesedo not demonstrate sufficient stability under extreme operating stress.

Proceeding from this situation, the invention is based on the task ofproviding crimps in the filter strip materials in such a way, andshaping them into filter elements with zig-zag-shaped folds, so thatgreat static stability of the folds of the filter element can beachieved, while at the same time, the filter material is not damaged bythe crimps.

This task is accomplished, for one thing, by the structure of the crimpshapes according to the characterizing section of claim 1, and foranother thing, by the arrangement and shape of the crimps within thestrip material, and its zig-zag folding to form a filter elementaccording to the characterizing sections of claims 7, 8 and 10.

Practical developments of the invention are the object of the secondaryclaims.

Embodiments of the invention are shown in the drawing. The drawingshows:

FIG. 1 a cross-section through a crimp running vertical to the plane ofthe filter strip

FIG. 2 a top view of a part of a filter material strip

FIG. 3 a cross-section through the filter material strip along LineIII--III on an enlarged scale

FIG. 4 a perspective view of a segment of a filter strip folded inzig-zag shape

FIG. 5 a view of the frontal side of a filter element folded in zig-zagshape

FIG. 6 a cross-section along Line VI--VI through the folds of the filterelement according to FIG. 5

FIG. 7 a view of the frontal side of an alternative embodiment of afilter element folded in zig-zag shape

FIG. 8 a cross-section along Line VIII--VIII through the folds of thefilter element according to FIG. 7

FIG. 9 a view of the frontal side of another embodiment of a filterelement folded in zig-zag shape

FIG. 10 a cross-section along Line X--X through the folds of the filterelement according to FIG. 9

In the crimp shown in cross-section in FIG. 1, the progression of thefunicular curve, which determines the shape of the curvature of thecrimp in this case, is entered with a dot-dash line.

A funicular curve is a mathematical concept and is defined by theprogression of a chain with an infinite number of links, under thestress of its own weight. Such a funicular curve is also called acatenary curve, in some instances.

By adapting the curvature of the crimp to the progression of a funicularcurve, a significant increase in inherent stability is achieved, ascompared with known crimp shapes.

In FIG. 1, H stands for the crimp height, B for the crimp width and Dfor the filter paper thickness.

In the embodiment according to FIG. 1, the filter material has athickness, in cross-sections placed perpendicular to the strip plane,which constantly decreases within the area of the crimps, starting fromthe non-deformed filter strip segments, to the zenith height H of thecrimp, with the filter material being compressed in the direction ofdecreasing thickness.

In this embodiment, a dimensional reduction in thickness in thedirection of the zenith height H of the crimp also exists perpendicularto the filter strip plane of a cross-sectional plane placed through acrimp.

In the case of a crimp directed longitudinally, the thickness is alwaysthe same, at least in the flanks opposite each other lateral to thelongitudinal direction, with the same vertical distance to thenon-deformed filter strip plane in each case.

The crimps have a width B within the non-stamped filter strip plane,which is in a ratio of less than 2 to the zenith height H.

At the zenith of the crimp shown in FIG. 1, the thickness of the filtermaterial is less than 80% of the thickness of the non-deformed filtermaterial. In the following, the filter strip material shown in FIG. 2-6and the way it is folded in zig-zag shape will be described.

The filter strip material 1 is provided with individual fold lineslateral to its longitudinal expanse, around which the strip material canbe folded in zig-zag shape. Double crimps are stamped into the stripmaterial at right angles to the fold lines 2. These double crimpsconsist of an upstream crimp 3 which will be on the upstream side of thefilter in readiness for use, and two downstream crimps 4 which willextend from the flanks of this crimp directly to the other side of thefilter strip.

The upstream crimp 3 extends farther out perpendicular on the materialstrip than the two downstream crimps 4 assigned to it.

When the filter material strip 1 is folded in zig-zag shape, theupstream crimps 3 of two adjacent fold segments lie together on theupstream side, while support is given via the smaller downstream crimps4 on the downstream side.

The arrangement of the crimps 3 and 4 allows symmetrical support of theindividual filter strip fold segments over the width of the filterstrip, especially on the downstream side. In this way, extremely securesupport against collapse of the filter strip fold segments can beachieved, while maintaining a large free filter surface.

The embodiment according to FIG. 7 and 8 is structured as follows. Thefilter strip material is laid in individual folds lateral to itslongitudinal expanse. The W-shaped crimps 5 alternate with V-shapedcrimps 6 in the longitudinal direction of the filter strip, at equalintervals. The unilateral elevation 7 of the W-shaped crimps 5 as wellas the V-shaped crimp 6 each project out of the filter strip material onthe upstream side.

The flow direction of the filter strip material is indicated by thearrows 8.

The folds are laid in such a way, in each case, that the downstreamelevations 9 of the crimp 5 rest against the foot of the V-shaped crimp6 on the downstream side.

The arrangement of the crimps 5 and 6 allows symmetrical support of theindividual filter strip fold segments, especially on the downstreamside. In this way, extremely secure support against collapse of thefilter strip segments can be achieved, while maintaining a large freefilter surface. In addition, greater flow space is available on theupstream side than on the downstream side, between the individual folds.

The embodiment according to FIG. 9 and 10 looks as follows.

The filter strip material 10 is folded in zig-zag shape lateral to itslongitudinal expanse. On the upstream and downstream sides, crimps 11and 12, respectively, project out of the filter strip. The flow-throughdirection of the filter material is marked with arrows 13. The folds ofthe strip material are laid in such a way that the crimps 11, whichproject out on the upstream side, rest against each other at their footareas on the downstream side and at their head area on the upstream sidein each case.

I claim:
 1. Strip-shaped filter material having a longitudinal planewith crimps molded therein for filtering a liquid or a gascomprisingfilter material being folded in a zig-zag shape and havingindividual fold segments; said individual fold segments being held at adistance from one another via the crimps; said filter material havingnon-deformed filter strip segments adjacent to each crimp; said crimphaving a zenith height; and the filter material having a thickness, in across-section placed perpendicular to the longitudinal plane of thestrip, which constantly decreases within the area of the crimps,starting from the non-deformed filter strip segments, up tot he zenithheight of the crimp, and that at the same time, the filter material isincreasingly compressed in the direction of decreasing thickness.
 2. Thefilter material according to claim 1,wherein in every cross-sectionalplane placed through a crimp perpendicular to the filter striplongitudinal plane, a dimensionally uniform reduction in thickness inthe direction of each zenith height of the individual crimp also exists.3. The filter material according to claim 2,wherein at the zenith ofeach crimp, the thickness of the filter material is less than 80% of thethickness of the non-deformed filter strip segments.
 4. The filtermaterial according to claim 1,wherein in the longitudinal direction ofthe crimp, the thickness is always the same; said filter material havingflanks between the crimps; and said flanks located opposite each otherlaterally to the longitudinal direction of the filter material, with thesame vertical distance from the flank to each non-deformed filter stripsegment.
 5. The filter material according to claim 1,wherein the crimpsare curved along a funicular curve at least in a cross-sectional planerunning perpendicular to the non-deformed filter strip, starting fromthe filter strip longitudinal plane.
 6. The filter material according toclaim 5,wherein the crimps have a width within the non-stamped filterstrip which is less than twice the zenith height.
 7. The filter elementmade of a strip of a relatively thin-walled filter material folded in azig-zag shape, which has lengthwise crimps according to claim 5 whichproject between the folded edges out of the longitudinal plane of thestrip, both on the upstream side and the downstream side, to hold thereciprocal distance of the folds, and in which non-deformed, levelsegments are between the crimps of the same fold surface;an upstreamcrimp which projects out of the filter material strip on the upstreamside; said upstream crimp having two longitudinal sides and passes over,at its two longitudinal sides, into a downstream crimp; said downstreamcrimp projects out of the other side of the filter material strip; eachupstream crimp being equal in height to all the upstream crimps; eachdownstream crimp being equal in height to all the downstream crimps;with the equal heights of the downstream crimps being smaller than theequal heights of the upstream crimps; and that adjacent strips restingon each other each touch against each other with their upstream crimps,on the one hand, and with their downstream crimps, on the other hand. 8.The filter element made of a strip of a relatively thin-walled filtermaterial folded in a zig-zag shape, which has lengthwise crimpsaccording to claim 5 which project between the folded edges out of thelongitudinal plane of the strip, both on the upstream side and thedownstream side, to hold the reciprocal distance of the folds, and inwhich non-deformed, level segments exist between the crimps of the samefold surface;said strip having two longitudinal sides; alternatingV-shaped and W-shaped crimps are arranged running alternately in thelongitudinal direction of the strip; each W-shaped crimp comprising anelevation which projects out of the filter material strip on theupstream side, which passes over, in each case, into and elevation whichprojects out of the filter material strip on the downstream side, ateach of its two longitudinal sides, with each of two downstreamelevations having the same height; the V-shaped crimps only projectingout of the filter material strip on the upstream side, with the spanwidth between the V-shanks at the transition of the filter strip beingless than or equal to the maximum span width between the long shanks ofthe W-shaped crimps, and; the fold lines are placed in such a way thatthe W-shaped crimps and the V-shaped always come to rest symmetricallyon top of each other.
 9. The filter element made of a strip of arelatively thin-walled filter material folded in a zig-zag shape, whichhas lengthwise crimps according to claim 5 adjacent to each other andpassing into each other in the filter strip longitudinal plane, whichproject between the folded edges out of the plane of the strip, both onthe upstream side and the downstream side, to reciprocally hold thedistance of the folds, and in which non-deformed level segments existbetween the adjacent pairs of crimps within the same fold surface;eachcrimp having a foot area on the downstream side and having a head areaon the upstream side; a folding of the filter strip material in whichthe crimps which project out on the upstream side rest against eachother at their foot areas on the downstream side and at their head areaon the upstream side in each case.
 10. The filter element of a strip ofa relatively thin-walled filter material folded in a zig-zag shape,which has lengthwise crimps according to claim 1, which project betweenthe folded edges out of the longitudinal plane of the strip both on theupstream side and the downstream side, to hold the reciprocal distanceof the folds, and in which non-deformed, level segments are between thecrimps of the same fold surface;an upstream crimp which projects out ofthe filter material strip on the upstream side; said upstream crimphaving two longitudinal sides and passes over, at its two longitudinalsides, into a downstream crimp; said downstream crimp projecting out ofthe other side of the filter material strip; each upstream crimp beingequal in height to all the upstream crimps; each downstream crimp beingequal in height to all the downstream crimps; with the equal heights ofthe downstream crimps being smaller than the equal heights of theupstream crimps; and that adjacent strips resting on each other eachtouch against each other with their upstream crimps, on the one hand,and with their downstream crimps, on the other hand.
 11. The filterelement made of a strip of a relatively thin-walled filter materialfolded in a zig-zag shape, which has lengthwise crimps according toclaim 1 which project between the folded edges out of the longitudinalplane of the strip, both on the upstream side and the downstream side,to hold the reciprocal distance of the folds, and in which non-deformed,level segments are between the crimps of the same fold surface;saidstrip having two longitudinal sides; alternating V-shaped and W-shapedcrimps are arranged running alternately in the longitudinal direction ofthe strip; each W-shaped crimp comprising an elevation which projectsout of the filter material strip on the upstream side, which passesover, in each case, int and elevation which projects out of the filtermaterial strip on the downstream side, at each of its two longitudinalsides, with each of two downstream elevations having the same height;the V-shaped crimps only projecting out of the filter material strip onthe upstream side, with the span width between the V-shanks at thetransition to the filter strip being less than or equal to the maximumspan width between the long shanks of the W-shaped crimps; and the foldlines are placed in such a way that the V-shaped crimps and the W-shapedcrimps always come to rest symmetrically on top of each other.
 12. Thefilter element according to claim 11,wherein the downstream V-crimp andW-crimp each projects from the filer material strip longitudinal planeto the same height.
 13. The filter element made of a strip of relativelythin-walled filter material folded in a zig-zag shape, which haslengthwise crimps according to claim 1, adjacent to each other andpassing into each other in the filter strip longitudinal plane, whichproject between the folded edges out of the plane of the strip, both onthe upstream side and the downstream side, to reciprocally hold thedistance of the folds, and in which non-deformed level segments existbetween the adjacent pairs of crimps within the same fold surface;eachcrimp having a foot area on the downstream side and having a head areaon the upstream side; a folding of the filter strip material in whichthe crimps which project out on the upstream side rest against eachother at their foot areas on the downstream side and at their head areaon the upstream side in each case.
 14. The filter element according toclaim 13,wherein the height of the crimps which project out on theupstream side is greater than that of the crimps which project out onthe downstream side.